Polyimides of olefin-maleic anhydride copolymers as diesel fuel additives



United States Patent O 3,471,458 POLYIMIDES F OLEFIN-MALEIC ANHY- DRIDE COPOLYMERS AS DIESEL FUEL ADDITIVES Enver Mehmedbasich, El Cerrito, Calif., assignor to Chevron Research Company, San Francisco, Calif, a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 554,994, June 3, 1966. This application Dec. 16, 1966, Ser. No. 602,124

Int. Cl. C08f 17/00; C101 1/22 US. Cl. 260-785 8 Claims ABSTRACT OF THE DISCLOSURE This application isa continuation-in-part of application Ser. Nos. 417,470, filed December 10, 1964 now abandoned, and 554,994, filed June 3, 1966, issued as U.S. Patent No. 3,413,104.

This invention concerns novel multifunctional fuel oil additives and fuel oil compositions thereof. More particularly, this invention concerns novel relatively low molecular weight polyimides and their use in fuel as dispersants and detergents.

Fuels are susceptible to chemical reaction on aging. The effect of oxidation is to produce soluble and insoluble materials of higher molecular weight and boiling point than the original fuel. The deterioration due to oxidation and the like of distillate fuels, particularly in diesel fuel, manifests itself, for example, through the appearance of color and gums. The tacky oxidized fuel deposits adhere readily to injector parts and can cause injector sticking, nozzle hole plugging and leakage past critical surfaces.

Also, diesel engines are equipped with fuel filters to remove particulate matter from the fuel. Any gums which are present in the fuel tend to coat onto the filter requiring frequent changes of the filter in order to permit adequate fuel flow as well as effective filtering action.

While many materials might effectively act as commercially successful dispersants for the gum, the field is severely limited to relatively few materials. For, since the dispersant is an additive to the fuel, it must not significantly increase the deposits created in the combustion chamber, which interfere with the proper functioning of the piston. In order to have an acceptable fuel dispersant, it is not only necessary that the dispersant maintain the gums dispersed in the fuel mixture, but the dispersant itself, when introduced into the combustion chamber should not form deposits which significantly interfere with the operation of the piston.

Pursuant to this invention, novel fuel dispersants are provided which are oil soluble alternating copolymers of N-substituted maleimides and aliphatic l-olefins of from 8 to 30 carbon atoms, more usually 10 to 24 carbon atoms, having from 4 to 20 maleimide groups. That is, succinimide group alternates with an alkyl substituted ethylene. The substituents on the nitrogen of the maleimide may be the same or different and are organic radicals composed solely of carbon, hydrogen and nitrogen having a total of from 3 to 60 carbon atoms and from 1 to amine nitrogen atoms. The substituents on the succinimide nitrogen can be aminoalkyl, polyamino alkylene or the mono-N- or di-N,N-aliphatic hydrocarbyl substituted derivatives thereof. (By the term aliphatic hydrocarbyl is intended organic radicals free of aromatic unwherein A is an organic radical of from 3 to 60 carbon atoms, more usually of from 3 to 30 carbon atoms having from 1 to 5 amine nitrogens and free of aromatic unsaturation. The symbol A includes aminoalkyl, polyalkylene amine, N-hydrocarbyl aminoalkyl N-hydrocarbyl polyalkylene amine and N,N-dihydrocarbyl aminoalkyl, wherein the hydrocarbyl groups are free of aromatic unsaturation. Usually, the hydrocarbyl groups will be aliphatic; that is, acylic, but may be alicyclic or taken together with the nitrogen, heterocyclic. R is an alkyl radical of from 6 to 28 carbon atoms, and n is an integer of from 4 to 20. Usually, R will be of from about 8 to carbon atoms, more usually from 12 to 18, and n from about 6 to 16.

One subgenus within the scope of the invention has the following formula:

CHCHOHr-CH 0 0 =0 R1 wherein T is aminohydrocarbyl free of aromatic unsaturation, generally of from 5 to 26 carbon atoms (aminohydrocarbyl free of aromatic unsaturation is a monovalent organic radical composed solely of carbon, hydrogen and one nitrogen, wherein the nitrogen is present only as primary, secondary or tertiary amines, and the radical is aliphatic, alicyclic or heterocyclic having nitrogen as its only annular heteroatom); R is an alkyl radical of from 6 to 28 carbon atoms, preferably of from 8 to 20 carbon atoms; n is an integer of from 4 to 20, inore usually of from 6 to 16.

: The particularly preferred compositions of the aminohydrocarbyl substituted compounds are those wherein the aminohydrocarbyl group is aliphatic of from 5 to 26 carbon atoms having one secondary nitrogen atom separated by not more than 6 carbon atoms from the succinimide nitrogen. The nitrogen atom may be part of the chain or may be pendant from the chain.

The polyalkylene amine compositions will have the following formula:

wherein B and B are alkylene of from 2 to 6 carbon atoms, more usually of from 2 to 3 carbon atoms, mis an integer of from 0 to 4, usually of from 0 to 3, R is an alkyl radical of from 6 to 28 carbon atoms, preferably of from 8 to 20 carbon atoms, and n? is an integer of from 4 to 20, more usually of from 6 to 16.

While, usually, the alkylene polyamines will be unsubstituted, if desired, substituted alkylene polyamines may be used having from 1 to 2 aliphatic hydrocarbyl substituents on the nitrogen atoms.

The remaining 2 valences of the polymer will be satisfied in a variety of ways. One or both of the valences may be satisfied by a radical derived from the polymer Patented Oct. 7, 1969 i 3 initiator. The polymeric chain may terminate by transfer, coupling or disproportionation, resulting in alkyl groups, alkenyl groups, succinimide or maleyl groups or radicals derived from the initiator.

Illustrative of various aminohydrocarbyl radicals are aminohexyl, aminodecyl, aminooctadecyl, N-hexylaminohexyl, N- decylaminopropyl, N-hexadecylaminohexyl, N- hexylpyrrolidinyl, N,N- diethylaminobutyl, N-abietyl 3- aminopropyl, N-dihydroabietyl 2- aminoethyl, etc.

Illustrative of various alkylene amine and polyalkylene polyamine radicals are tetraethylenyl tetraminc, triethylenyl triamine, diethylenyl diamine, dipropenyl diamine, tripropenyl triamine, etc.

A particularly preferred group of compounds have repeating units of the formula:

IIIH

wherein R is an alkyl radical of from 8 to 20 carbon atoms, m is an integer of from 2 to 3, C indicates an aliphatic hydrocarbon radical having x number of carbon atoms wherein x is an integer of from 8 to 20, i.e., C and n is an integer of from 6 to 16. The aliphatic radical may be straight chain or branched, free of aliphatic unsaturation or unsaturated, particularly olefinically unsaturated.

Illustrative of the particularly preferred substituents on the succinimide nitrogen are N-octyl 3-aminopropyl, N-decyl 2-aminoethyl, N-dodecyl 2-aminoethyl, N-hexadecenyl 2- aminoethyl, N-octadecenyl 3- aminopropyl, N-tetradecyl 2- aminoethyl, N-eicosenyl 3-aminopropyl, N-tetrapropenyl Z-aminoethyl, N-octadecadienyl Z-aminoethyl, N-hexadecenyl 3-aminopropyl, N-octadecyl 3-aminopropyl, N-octadecenyl 2-aminoethyl, etc.

The compounds of this invention are readily prepared by copolymerizing an aliphatic l-olefin of from 8 to 30 carbon atoms with maleic anhydride by means of free radical catalysis and then combining the resulting polymer with the desired amine at elevated temperatures to form the alternating N-substituted polysuccinimide.

The copolymerization of maleic anhydride with aliphatic l-olefins is well known in the art. See for example U.S. Patent No. 3,051,562.

The olefins which find use include decene, dodecene;

tetradecene, hexadecene, octadecene, eicosene, docosene, tetracosene, haxacosene. octacosene, triacontene, tridecene, pentadecene, heptadecene, nonadecene, tetrapropylene, tetraisobutylene, hexapropylene, etc. Preferably, a mixture of olefins will be used rather than a single olefin. When using mixed olefins, superior fuel solubility is obtained. The mixture will generally have not more than 50 percent of any single olefin, and preferably not more than 30 mole percent of any single olefin.

The free radical catalyst may be any organic compound which at a temperature in the range of 50 to 100 C. decomposes to form free radicals which may then initiate the polymeric chain, although temperatures outside this range may be used advantageously under some conditions. The most popular organic free radical agents are the peroxidic initiators-hydroperoxide, dihydrocarbyl peroxide, and diacyl peroxide and azo compounds. Illustrative of hydroperoxide catalysts are cumyl hydroperoxide, pinane hydroperoxide, tert.-butyl hydroperoxide, p-menthan hydroperoxide, etc. Illustrative of dihydrocarbyl peroxides are dicumyl peroxide, ascaridole, di-tert.-buty1 peroxide, etc. Illustrative of diacyl peroxides are benzoyl peroxide, lauroyl peroxide, acetyl peroxide, 2,4-dichlorobenzoyl peroxide, etc.

In carrying out the various polymerizations, inert hydrocarbons or halohydrocarbons may be used to advan- 4 tage. Illustrative of such solvents are benzene, toluene, chlorobenzene, etc.

Usually, the solvent will be from 20 to weight percent of the total reaction mixture, more usually about 30 to 70 weight percent.

The mole ratio of wolefin to maleic anhydride will generally be about 0.9-1.2:l.20.9, more usually about 1:1. The ratio of olefin to catalyst will generally be 1:0.005-0.1 mole ratio, more usually l:0.01-0.1 mole ratio.

As already indicated, the temperatures will depend upon the catalyst. Temperatures in the range of 50 to C. may be used; more usually the temperature will be in the range of about 75 to 95 C. The time for the reaction will depend on the catalyst used, the amount of material, and the other variables. Generally, at least one hour will be required, and usually the reaction will not be carried out for more than a period of 24 hours.

Depending on the amount of the materials, the catalyst may be added in a single addition or in aliquot portions during the course of the reaction, maintaining a relatively constant concentration of free radicals in the reaction mixture.

The reaction of the copolymer with the relevant amine is readily carried out by combining the copolymer with the amine in an inert hydrocarbon solvent at elevated temperatures (50-150 C.) and removing the water as formed. Preferably, an aromatic hydrocarbon solvent is used which allows for azeotroping the water. When the stoichiometric amount of water has been obtained, the reaction is stopped.

The following examples are offered by way of illustration and not by way of limitation.

Example A Into a reaction flask was introduced 243 g. (1.0 mole) of C1540 cracked wax l-olefins 98 g. 1.0 mole) of maleic anhydride and 341 g. of benzene. The mixture was stirred at a temperature of F. and 9.7 g. (0.04 mole) of benzoyl peroxide and a minimum of benzene added. The solution was then heated at F. for 12 hours The reaction product was precipitated with methanol and redissolved in benzene. The yield was 290 g. (85%). The product was characterized by its infrared spectrum.

N0. of carbon atoms l-olefin Straight chain 86 Example I Example II Into a reaction flask was introduced 341 g. (1 mole) of a 50 weight percent solution of copolymer prepared as in Example A in benzene and 102.1 g. (1 mole) of dimethylaminopropylamlne and diluted with 84 g. of xylene. After heating the mixture for 6 hours at 80 to 90 C., one mole of water was obtained. The product was then isolated and characterized by its infrared spectrum. The characteristic succinimide absorption was found.

Example III Into a reaction flask was introduced 72.1 g. (0.38 mole) of a mixture having as the major component and the average composition tetraethylene pentamine, 185 g. of xylene and 185 g. of an aromatic thinner. This mixture was heated to 115 C. and 131 g. (0.38 mole) of copolymer prepared as in Example A dissolved in 300 g. of xylene added slowly over a period of 4 hours. After maintaining a temperature of 130 C. for 4 hours, the stoichiometric amount of water was azeotroped off. The product was characterized by its infrared spectrum.

The novel compositions of this invention find use, par- A second stability test was carried out by heating the fuel for hours at 200 F. The fuel was then cooled at ambient temperature for 24 hours and filtered through a tared S-micron pore size Millipore membrane filter. The filter is then weighed and the results are shown as parts per million of filter residue.

Finally, a long-term storage test was carried out by aging the fuels for 4 weeks at 140 F. and then cooling, followed by filtering the cooled, aged fuel through a tared S-micron pore size Millipore membrane filter. The filter is then weighed, and the results are shown as parts per million of filter residue.

The fuel used was a 70% catalytically cracked light cycle oil plus vacuum top-cut straight run. The following table indicates the results.

TAB LE I Santa Fe 20 hours, 200 F. 4 weeks, 140 F. stability Concen- Initial test, Filter Filter tration, ASTM 1 percent residue, ASTM residue, ASTM Additive p.p.m. color reflectance 2 p.p.m. color p.p.m. color Fresh Fuel:

None 1. 5 10 5. 5 37 6. 5 Ex. I. 25 l. 5 3 5.0 29 L7. 0 Ex. I 100 1. 5 4 L4. 5 6 L7. 0 Ex. I. 200 1.5 3 L4. 5 4 7.0 Comm al Ad e 100 1. 5 3 5. 0 26 L7. 0 Cornnlieicial Additive B 200 1. 5 9 L5. 5 42 6. 5

Aged Fuel B:

1 ASTM N0. D1500,

58T. 2 Pass, above 73, Borderline, 53-72, Reject, below 52.

ticularly with compression ignition engines, e.g., diesel engines. The compositions are readily compatible with a variety of fuels and may be prepared as concentrates or at concentrations to be used directly in the engine. As concentrates, concentrations in the range of 25 to 75% find use, while in the engine, the additive concentration will be in the range from about 10 to 2000 p.p.m., more usually in the range of about 25 to 250 p.p.m.

The base fuel which may be used, in accordance with the invention, may be a straight run or a cracked petroleum distillate; or a residual fuel; or it may be a fuel derived from shale; or one produced synthetically, for instance, by the Fischer-Tropsch process. It may also be a mixture of two or more of the aforementioned fuels. The base fuels used boil in the range from about 325 to 750 F. In other words, they are suitable for use in engines of the diesel type, and the like.

In order to demonstrate the excellent disperancy of the compositions of this invention, the exemplary compositions were tested under a variety of generally accepted tests which determine the acceptability of a composition as a dispersant. Both fresh fuel and fuel which had been allowed to age for a considerable length of time were tested, comparing fuel compositions containing the exemplary additives of this invention and the same fuel composition without the exemplary additives.

An accelerated stability test, known as the Santa Fe Stability Test, comprises heating a sample fuel for 90 minutes at 300 F., cooling at ambient temperatures for 90 minutes, and then filtering through a Whatman No. l filter paper. The appearance of the deposits on the filter is rated by a reflectometer on a rating scale of 100% reflectance for a new white filter and 0% reflectance for a completely black filter.

It is evident from the above data that the dispersants of this invention prevent the formation of material which would interfere with engine filters, while at the same time maintaining excellent color stability, the latter, particularly important for pipeline transport.

The following test was carried out to determine the capability of the subject compositions in maintaining the nozzle injector free of deposits. The test uses a modified CFR diesel engine where the fuel injector system has the nozzle cooling restricted in order to increase the severity of the test. The injector deposits obtained in this test are rated with the aid of a refiectometer. The results of this test are reported as percent deposits relative to base fuel without additive.

TABLE II Relative Concentration, injector Additive p.p.m; deposits Ex. I 200 84 visual inspection was the state of the plungers and cups as Well as the smoke.

2. A copolymer having as the repeating group a unit of the following structure:

TABLE III Exhaust Injector Conditions Smoke,

percent Concen- Start End Filter tration, of of deposits, Additive p.p.m. Plunger Cups run test grams None Heavy dcposits Heavy internal and tip deposits with 2 6 25.0

some holes plugged and distorted.

Ex. I 100 Light deposits Light internal deposits and moderate 4 3 0.9

tip deposits. No plugged holes.

TABLE IV Groove Land Cone. deposits deposits Additive:

The deposit data show that the compounds of this invention do not have any adverse effect on piston deposits. They further show that the compounds of this invention are compatible with conventional fuels.

The compounds of this invention were also found to provide excellent rust inhibition and good water tolerance. Therefore, the compounds of this invention provide a variety of improvements to fuels with a minimum, or absence of deleterious effects.

Other additives may also be included in the fuel in combination with the present additives, so as to provide further improvements; such additives include antioxidants, metal deactivators and cetane improvers.

The compositions of this invention are compatible with the trace contaminants usually found in fuels, particularly diesel fuels. Illustrative of such contaminants are naphthenic acids found in middle distillate fuels. The basic amine nitrogen of the compositions of this invention will probably, in the presence of naphthenic or other sufficiently acidic material, form salts, e.g., naphthenates. Therefore, the compositions of this invention may be present in the fuel in the form, in whole or in part, as ammonium naphthenate salts. However, the formation of the naphthenate salts does not significantly affect the eflicacy of the compositions of this invention as detergents.

As will be evident to those skilled in the art, various modifications on this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.

I claim:

1. An alternating copolymer consisting essentially of aliphatic l-olefins of from 8 to 30 carbon atoms and N-substituted maleimides, wherein the N-substituents on the maleimides are organic radicals free of aromatic unsaturation having from 3 to 60 carbon atoms and from 1 to 5 amine nitrogen atoms, and wherein said copolymer has from 4 to repeating units.

wherein A in an organic radical of from 3 to 60 carbon atoms, free of aromatic unsaturation and having from 1 to 5 amine nitrogen atoms, R is an alkyl radical of from 6 to 28 carbon atoms and n is an integer of from 4 to 20. 3. A composition according to claim 2, wherein R is an alkyl radical of from 8 to 20 carbon atoms and n is an integer of from 6 to 16.

4. A copolymer having as a repeating unit the following formula:

CHCHCHzOH- O=C C=O l t l B(NHB )mNHg 1 I ZM IIIH wherein R is an alkyl radical of from 8 to 20 carbon atoms, m is an integer of from 2 to 3, C is an aliphatic hydrocarbon radical having x number of carbon atoms wherein x is an integer of from 8 to 20, and n is an integer of from 6 to 16.

7. A copolymer according to claim 6, wherein m is 2 and x is 18.

8. A copolymer according to claim 6, wherein C is a straight chain aliphatic hydrocarbon radical.

References Cited UNITED STATES PATENTS 2,698,316 12/1954 Giammaria 26078.5 XR 2,977,334 3/1961 Zopf et al 260-78.5 XR 3,010,810 11/1961 Stayner et a1. 4462 3,235,503 2/1966 Devries 25'251.5

JOSEPH L. SCHOFER, Primary Examiner JOHN KIGHT, Assistant Examiner 

